 
   These handlers take two arguments;  `coeffects` and `event`, and they return `effects`.
 
-  (fn [coeffects event]
-     {:db ...
-      :dispatch ...})
+      (fn [coeffects event]
+         {:db ...
+          :dispatch ...})
 
    Wrap handler in an interceptor so it can be added to (the RHS) of a chain:
      1. extracts `:coeffects`


  These handlers take two arguments;  `db` and `event`, and they return `db`.

  (fn [db event]
     ....)

  So, the interceptor wraps the given handler:
     1. extracts two `:coeffects` keys: db and event

  can be slow. So, you won't want this interceptor present in production
  code. So condition it out like this :

      (re-frame.core/reg-event-db
         :evt-id
         [(when ^boolean goog.DEBUG re-frame.core/debug)]  ;; <-- conditional
         (fn [db v]
           ...))

  To make this code fragment work, you'll also have to set goog.DEBUG to
  false in your production builds - look in `project.clj` of /examples/todomvc.
